This is the only Pipa toad to occur in North America. With its warty, filamented skin and flat, sunken body, it has the uncanny ability to look almost putrefied even when at the peak of good health. One bizarre adaptation is the tactile organs or lobes present on the fingertips, which are used to explore the surrounding water and mud for aquatic invertebrates, crustaceans and fish. Unusually, Surinam toads cannot assume the "standard" terrestrial-frog posture, with the forelimbs holding the body up slightly and their legs folded either side of their abdomen. Their resting position is instead characterised by their arms and legs splaying outwards in line with their flattened body.

Urgent Conservation Actions

Further research is needed into the range, ecology and potential conservation measures for the species.

The original Myer's Surinam toad that was discovered by scientists was collected 7 km from the mouth of the Rio Ucurganti, Provincia Darien, Panama between the 21st and 25th November 1965 by C.W. Myers and Tomas Quintero.

Juvenile pipid toads from the lowlands of eastern Panama were initially assigned to the species Pipa parva (the Sabana Surinam toad of Colombia and northeastern Venezuela) by Harold Heatwole in 1963. Examination of these specimens some years later led to them being assigned to their own separate species, Pipa myersi or Myer's Surinam toad, in 1984. Myer's Surinam toad may be distinguished from other pipids by the fact that they only have two major lobes on the tips of their fingers (with a stumpy medial lobe in the centre), whereas Pipa parva has four large lobes. Additionally, the young of Pipa parva emerge from the mother’s back as fully formed froglets instead of tadpoles, as is the case with Myer’s Surinam toad.

Although it was originally misidentified by the collectors as the Sabana Surinam toad, the new species was later renamed from the Old Norse word myrr, meaning bog, swamp or deep mud, in reference to the preferred habitat of this species. Not coincidentally, the scientific name is also a tribute to one of the scientists that originally collected this species, Charles W. Myers (Myers derived from the French myre, meaning "keeper of the swamp").

Pipid toads are known to have the ability to regenerate parts of their body. Two of Myer’s Surinam toad’s close relatives, Pipa arrabali and Pipa pipa, have been observed regenerating severed toes and/or fingers.

Live Surinam toads cannot assume the "standard" terrestrial-frog posture, with the forelimbs holding the body up slightly and their legs folded either side of their abdomen. Their resting position is instead characterised by their arms and legs splaying outwards in line with their flatterned body. They can, however, move surprisingly quickly across a dry surface, as anyone who has ever chased an escapee around the room can testify.

Evolutionary Distinctiveness

Order: Anura

Family: Pipidae

The family Pipidae is also referred to as the “tongueless frogs” or “clawed frogs”. Pipids are highly aquatic frogs that rarely, if ever, venture out of water. They have several adaptations to aquatic life, including the loss of the tongue (tongues are not generally useful for feeding in water), and the presence of lateral line organs, which are used to detection wave motion in water and are present in most groups of fishes (however, this lateral line system is unusually absent in Myer’s Surinam toad adults). The group is sometimes also referred to as the “Aglossa”, which means “without a tongue”. Many species in this family possess a bony voice box with two cartilaginous rods that produce a clicking sound, signaling their presence to their neighbours and/or the male’s will to mate.

The pipids are present in a small sub group of the Anura or “frogs and toads” which contains all of the most ancient families. This sub group (also called the Archaeobatrachia) comprises less than 7% of all of the frogs and toads, including some of the most evolutionarily distinct amphibian species. The pipids diverged from all other amphibians over 130 million years ago in the Creataceous period, which is around the same time that the first evidence of flowering plants dates from. The Pipa toads are thought to be the earliest family to have diverged within this group, breaking away from its close relatives some 120 million years ago. Myer’s Surinam toad therefore belongs to one of the most evolutionarily distinct genera within the “frogs and toads”, and is the only Pipa toad to occur in North America.

As a testament to their high degree of evolutionary distinctiveness, Pipa toads have arguably the strangest and most elaborate of all amphibian mating behavior, in which eggs are deposited on the back of the female and the skin swells up around the eggs to encase them in pockets in which the embryos develop. In some species the eggs hatch out as tadpoles, but in others the tadpoles are retained in the mother’s back tissues, emerging as fully formed froglets a little later on.

Juvenile pipid toads from the lowlands of eastern Panama were originally assigned to the species Pipa parva (the Sabana Surinam Toad of Colombia and northeastern Venezuela) by Harold Heatwole in 1963. Examination of these specimens some years later led to them being assigned to their own separate species, Pipa myersi or Myer's Surinam toad, in 1984. Myer's Surinam toad may be distinguished from other pipids by the fact that they only have two major lobes on the tips of their toes (with a stumpier medial lobe in the centre), whereas the Sabana Surinam toad has four.

Description

In his 1954 book “Three Tickets to Adventure”, the naturalist Gerald Durrell described a large female Surinam toad with the words:

"…looking – as all pipa toads look in repose – as though she had been dead for some weeks and was already partially decomposed."

For those unfamiliar with the appearance of the Surinam toads, this provides a perfectly adequate description since these creatures, with their warty, filamented skin and flat, sunken bodies, have the uncanny ability to look almost putrefied even when they are at the peak of good health.

Of the five species of pipid toad, Myer’s Surinam toad is fairly small in size, meauring 36-45 mm in length. The most well-known and widely ranging pipid toad, the Surinam toad (Pipa pipa), can reach four times this size with the largest females reaching 171 mm in length. Myer’s Surinam toad is flattened in appearence, with the head being narrower than the body and triangular in shape. Adults lack both teeth and tongues, and no clear subdivision is evident between the head and body. Limbs are stout and moderately short and the toes nearly fully webbed. Hind limbs are much stronger than fore limbs as an adaptation for swimming. Their long fingers are very odd – they have highly sensitive tips which are forked into lobes, explaining why Pipa toads are also commonly referred to as the star-fingered toads. These lobes act as miniscule "feelers" used to detect prey. Under microscopic inspection, these lobes can be seen to continue to divide into smaller ends.

The skin of Myer’s Surinam toad is highly verrucose (or warty) and, like its close relatives, tends to have an eerie look of decay about it. The back of this species is a dark greyish-black, whilst the stomach is a dirty, yellowish grey. The eyes are pale bronze with blackish-brown spotting and do not posses eyelids. Female pipid toads are generally larger than the males, and can also be distinguished by a ring-shaped swelling at the cloaca (or reproductive / urino-genital opening), visible only when they are ready to breed.

The tadpoles are dark grey, with silvery white underside. They have developed tail fins but do not have keratinised mouth parts (i.e. they do not have mouth parts strengthened with keratin, which is the same material that forms human nails and hair) or barbels either side of the mouth, which are common in other species within the Pipidae family. The body is less than one-third the total length of the tadpole.

Ecology

This is an entirely aquatic amphibian, spending its whole life cycle in shallow pools within its swampy habitat. Although it has been little-studied, much of its life history may be extrapolated from what is known of its close relatives, such as the wide-ranging and common Surinam toad (Pipa pipa), which was originally described by Carl Linnaeus (the founder of modern taxonomy) over 200 years before the discovery of Myer’s Surinam toad.

The body of this species is highly adapted for its aquatic lifestyle. Pipa toads possess much reduced eyes and rely more on their other senses when hunting their prey. One especially bizarre adaptation is the tactile organs or lobes present on the fingertips, which are used to detect food. These toes are use to explore the surrounding water and mud for aquatic invertebrates, crustaceans and fish (if present). When detected by the fingertips, the prey is taken into the mouth of the toad, which (though toothless and tongueless) has an enormous gape. Prey items may be eaten using a "vacuum cleaner" technique in which the frog opens its mouth and expands its body, sucking in the prey item into the mouth in a rush of water. The water and any unwanted detritus (such as gravel) are then expelled moments later. Inanimate food or prey items with limited mobility may simply be crammed into the mouth using the hands and ingested with a "snapping" motion.

The reproductive habits of the Pipa toads feature elaborate breeding behaviours unlike anything else discovered in the animal kingdom. These behaviours have been most closely observed in the Surinam toad (Pipa pipa) but are probably similar for the related species of Pipa toads. Mating begins when males make a metallic trilling or clicking call in the water. Males then move to grasp the female from above in an “inguinal amplexus” (the mating embrace) around the lower part of her body, just above the legs. If she is not receptive, she quivers until released but if the female is ready the clasp may be maintained for more than a day. During this time, the skin of the female's back becomes puffy as the blood supply is increased. Just prior to egg laying, the pair start to turn over repeatedly in backward somersaults through the water. This action is effected mostly by the female. The eggs start to be released during the middle phase of the somersault when the pair is upside down in the water. As the eggs emerge, they are more or less caught by the belly of the male and as the pair flip over, the eggs are caught by the skin on the back of the female and adhere there whilst the male releases sperm to fertilise them. The entire turn-over process takes 11-14 seconds. The spawning ritual is repeated 15-18 times and 40-200 eggs are released, with the average generally being 100. If this process is not perfectly synchronised, the eggs fall to the bottom of the pool and are lost. Captive studies have observed losses of about 20% of the eggs during this process.

During the upward phase of the turnover, the male may be observed massaging the belly of the female with his long fingers, perhaps stimulating her to expel eggs. The eggs themselves are not sticky. It is the skin on the back of the female that attaches to the surface of the eggs and the male will facilitate this attachment by pressing the eggs into place.

The development of the eggs is a slow process. They sink gradually into the skin of the female's back, becoming level with the surface of the skin after about ten days, and some eggs may be crowded out and lost during this period. The outermost egg membrane forms a cap for the brood pocket (or "cell") in which the eggs develop. This cap soon becomes covered with debris so that it is difficult to see what is happening to the egg. By the middle of the fourth week, the embryo is able to move within its brood pocket. When in the tadpole stage, the tail serves a similar purpose to a placenta in mammalian embryos. It is rich in capillaries (or tiny blood vessels) and facilitates the uptake of oxygen from the walls of the brood pocket, which are also abundantly supplied with blood vessels.

In the Surinam toad (Pipa pipa) and the other species of Pipa toad that retain their young until they have metamorphosed into froglets, the tail is reabsorbed at least three weeks before the young leave the mother’s back. Oxygen uptake will then occur predominantly through the skin of the growing froglet. Myer’s Surinam toad is slightly different in that the young hatch from the mother’s back whilst still in the tadpole form. Judging from the dry weights of the young and eggs, there does not seem to be any passage of nutrients between the mother and her young in Pipa toads beyond the provision of a yolk supply present when the eggs are laid. The froglets emerge 77 to 136 days after egg-laying. The period of time taken for Myer's Surinam toad to release its tadpoles is probably shorter because the young are released at an earlier stage in their development. Emergence of the young seems to be partially related to skin-shedding by the mother. Cell caps are often lost first during skin shedding. In the species that release their young as froglets, the young may start to poke legs, arms and snouts out of the opening. The female will also exert internal pressure along the bases of the brood pockets for a minute or two at a time. This action, combined with further skin shedding, may hinder oxygen exchange within the cell and eventually the froglets or tadpoles (depending on the species) seem to exit the brood pockets of their own volition.

In observations of the Surinam toad, the mother has not been seen to eat her own young, which is strange because usually any small, moving object that touches the toad's fingers is swept up into its mouth. In fact, a batch of young was left in the same tank as the mother for over two months without her attempting to eat them. Presumably, this curb on the mother's normal feeding behaviour may have selectively evolved as mothers that recognised and did not eat their own offspring had a greater net breeding success than mothers that ate their young and therefore forfeited some of their breeding success.

Upon hatching from their mother’s back, tadpoles of Myer’s Surinam toad are more common at the surface of the water at night than by day. However, metamorphosing young are only visible when they swim to the surface to gulp air before descending to hide amongst the leaf litter at the bottom of the swamp.

In the wild, the animals space themselves using calls to communicate location and distance. Surinam toads (Pipa pipa) are usually quiet and still, resting on each other without disturbances. They lie on the muddy bottom of the water body, returning to the surface to gulp air into their lungs every half hour or so. They do not leave the water voluntarily. Male Surinam toads make single clicking sounds during fights or to challenge territory. In a captive environment they have also been observed to charge into each other, butt heads, “bite” and kick.

Habitat

An aquatic species restricted to swamps and other suitable wetlands such as lowland forest swamps containing abundant leaves and clear, but brown-coloured water. The location from which specimens have been collected has flat land characterised by ox-bow lakes and frequent shallow swamps and pools that lack fish, probably because they result from the collection of rainfall within depressions in the ground rather than river flooding. The swamp in the area where this species was originally found at the Rio Ucurgantí had a maximum depth of one metre, and the other location for this species at the Rio Canclon was only 1.5 m in diameter and 20 cm deep.

Distribution

This species has been recorded from the Rio Ucurgantí and Rio Canglon of Darien Province, Panama, and tentatively from Río Zulia in Norde de Santander, in northern Colombia. This is a lowland species occurring up to 30m above sea level.

There is no information available on the population size or abundance of this species.

Population Trend

Myer’s Surinam toad is considered to be in decline by the IUCN Red List of Threatened Species.

Status

Listed as Endangered on the IUCN Red List of Threatened Species because its extent of occurrence is less than 5,000 km sq., its distribution is severely fragmented, and there is continuing decline in the extent and quality of its habitat in Panama.

Threats

Habitat loss by the destruction of forests surrounding wetlands and water pollution.

Conservation Underway

Although there are no specific conservation measures in place, the species has been recorded from a protected area (Reserva Canclon Hidrologica) in Panama.

Conservation Proposed

Further research is needed into the range, ecology and potential conservation measures for the species.